Left midcardiac border of frontal chest radiographs of patients with annulo-aortic ectasia.

The utility of the frontal chest radiograph for the diagnosis of annulo-aortic ectasia (AAE) was evaluated in 12 patients with Marfan's syndrome and five patients with incomplete stigmata (forme fruste). Prominence of the left midcardiac border was seen in 11 patients: the upper midsegment in one, the lower midsegment in two, and the whole midsegment in eight patients. Either a linear or an arcuate contour was seen. The contours of the prominent left midcardiac border in three patients who had moderate to marked aortic regurgitation and a cardiothoracic ratio (CTR) over 59% were nonspecific. In the remaining eight patients (47%), the contour was considered to be characteristic of AAE, as suggested by the displacement of either all or part of the right ventricular outflow tract, main pulmonary artery and left atrial appendage. Six patients showed only left midcardiac border prominence. The contour of the left midcardiac border on the conventional frontal chest radiograph is characteristic and of paramount importance for the diagnosis of AAE in Marfan' s syndrome or its forme fruste, particularly in patients whose CTRs are within the normal range.